Suddenly runs rough, no tach

[danny]

Thanks for the ideas!
There aren't any ignitors. I double checked, those seem to have started in 1980.
I did check the fuel filter. It is new as well, maybe 100-200 miles with it so far. It looks clean. I will take a look at the fuel pump. I guess I would listen to it? What's interesting is that it doesn't stall and it's a bit rough from idle to 3K rpm or so, but really rough after 4K, with no power.

The vacuum leak is what I was thinking. I've looked already, but will take an even closer look. Danny, what seal are you referring to? And you noticed it just by cleaning the engine in the car?

Much appreciate everyone!!

Well, it was a little more than a good clean. It is the gasket between the intake manifold and the engineblock that was rotten. The O-rings must also always be replaced.

[Onen]

Awesome picture! So I removed the stock exhaust and put a header (Racing Beats), and block off plates on, with a sealant. The mating surfaces were very clean. I'm going to look at this area where there hasn't been anything removed or blocked.

At this point I do think I'm chasing a vacuum leak. This is a good place to check.

Appreciate it, as always!!